Geochemical surveillance of the Solfatara of Pozzuoli (Phlegraean Fields) during 1983

Geochemical surveillance of the Phlegraean Fields area has been intensified since 1983, in response to the increased uplift rate (brady-seismic activity).Fumarolic gases from Solfatara (Pozzuoli) were sampled and analyzed monthly. A Reducing Capacity (RC) monitoring unit was installed at Soffione, the most active fumarole in the Solfatara system.The preliminary analysis of the RC temporal variations suggest they are consistent with the rate of the seismic energy release.The composition of fumarolic gases indicates that the equilibrium temperature and pressure are higher than those of sampling.The observed variations in CH₄ content are explained as an increase of pressure (from 1982 to the end of 1983) of about 70% at an extimated depth of 3–3.5 km.Finally, during 1983, there were no geochemical indications of both rising magma and significant accumulation of energy at shallow depth.